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We obtained the spectrum of probability of the bremsstrahlung emission accompanying the α-decay of 226 Ra (Eα=4.8 MeV) by measuring the α-γ coincidences and using the model presented in our previous study on the α−decay of 214 Po (Eα=7.7 MeV). We compare the experimental data with the quantum mechanical calculation and find a good agreement between theory and experiment. We discuss the differences between the photon spectra connected with the α-decay of the 226 Ra and 214 Po nuclei. For the two mentioned nuclei we analyze the bremsstrahlung emission contributions from the tunneling and external regions of the nucleus barrier into the total spectrum, and we find the destructive interference between these contributions. We also find that the emission of photons during tunneling of the α-particle gives an important contribution to the bremsstrahlung spectrum in the whole Eγ energy range of the studied 226 Ra nucleus.

This paper is dedicated to the memory of Dr. Ivan Egorovich Kashuba -a brilliant scientist with bright nature who worked in science till his last days. Abstract.A new quantum electrodynamical method of calculations of bremsstrahlung spectra in the α-decay of heavy nuclei taking into account the angle between the directions of α-particle motion (or its tunneling) and photon emission is presented. The angular bremsstrahlung spectra for 210 Po have been obtained for the first time. According to calculations, the bremsstrahlung in the α-decay of this nucleus depends extremely weakly on the angle. Taking into account nuclear forces, such dependence is not changed visibly. An analytical formula of the angular dependence of the bremsstrahlung spectra is proposed and gives its harmonic behavior. The extremal values of the angle, at which the bremsstrahlung has maximal and minimal values, has been found.

A quantum mechanical model for the description of the α-decay of heavy nuclei with accompanying photons emission is presented. The model is based on a quantum mechanical one-particle model of α-decay through a decay barrier. The bremsstrahlung spectrum calculation employs multipole expansion of the vector potential of the Coulomb field of the daughter nucleus and takes into account the dependence on the angle between the directions of the α-particle propagation and the photon emission. Spectra of 210 Po are obtained for the angles 25 • and 90 • , and the best agreement with the experimental data in the 90 • case in a comparison with other existing models is achieved. From the angular analysis, the model gives monotonic behavior of the bremsstrahlung spectrum for any value of the angle. We find that sub-barrier photon emission (i. e. bremsstrahlung photon emission during αparticle tunneling through decay barrier) exists but gives a small contribution to the total bremsstrahlung spectrum. * )

A model of the bremsstrahlung emission which accompanies proton decay and collisions of protons off nuclei in the low-to intermediate-energy region has been developed. This model includes spin formalism, a potential approach for describing the interaction between protons and nuclei, and an emission that includes a component of the magnetic emission (defined on the basis of the Pauli equation). For the problem of bremsstrahlung during proton decay the role of magnetic emission is studied by using such a model. For the 146 Tm nucleus the following has been studied: (1) How much does the magnetic emission change the full bremsstrahlung spectrum? (2) At which angle is the magnetic emission the most intensive relative to the electric emission? (3) Is there some spatial region where the magnetic emission increases strongly relative to the electric emission? (4) How intensive is the magnetic emission in the tunneling region? (5) Which is the maximal probability? Which value does it equal to at the zero-energy limit of the emitted photons? It is demonstrated that the model is able to describe well enough experimental data of bremsstrahlung emission which accompanies collisions of protons off 9 C, 64 Cu, and 107 Ag nuclei at an incident energy of T lab = 72 MeV (at a photon energy up to 60 MeV) and off 9 Be, 12 C, and 208 Pb nuclei at an incident energy of T lab = 140 MeV (at a photon energy up to 120 MeV).